Dynamic adsorption of water-soluble and insoluble vapours on activated carbon

Dynamic adsorption of organic vapours on humidified carbon beds was studied in order to examine the effect of water-solubility on the adsorption. The carbon beds were pre-loaded with water and the adsorption was carried out at two relative humidities (RH), that is, 73 and 89%. At the higher humidity, the water content of the carbon was ca 40 wt% and there was >90% drop in the service time for each adsorbate as compared to dry carbon. At RH of 73%, where the amount of water was ca 20 wt%, the drop in service time changed with the type of the adsorbate. Molecules with high affinity to the carbon surface, whether soluble or not, were less influenced by the presence of water. Solubility was not found to be a prominent factor which affects the adsorption on a wet carbon bed. It is suggested that with carbon treated at 73% RH, adsorption starts on dry surface and proceeds by replacing adsorbed water, rather than by direct diffusion through condensed water in the pores. (C) 1998 Elsevier Science Ltd. All rights reserved.